This invention relates generally to radio frequency switches and more particularly to coaxial transmission line switches.
As is known in the art, one type of coaxial transmission line switch includes a rotatable coupling element in contact with the center conductor of an input coaxial transmission line and adapted for contacting the center conductor of a selected one of a plurality of output coaxial transmission lines. Such switch is described in "Microwave Transmission Circuits" edited by George L. Ragan, published and distributed by Boston Technical Publishers, Inc., 5 Bryant Road, Lexington, Mass. 02173, 1974 edition. While such type of coaxial transmission line switch has been found adequate in many applications, the power handling capability and life of such type of coaxial transmission line switch is limited because of the possibility of voltage breakdown resulting from metal shavings from the contacting center conductors being present in the region of strong radio frequency fields.
It is also known in the art that it is sometimes desirable to form filters from sections of coaxial transmission lines. Such filters may be formed because, at radio frequencies, a capacitor may be realized in a coaxial transmission line by a series gap in the center conductor of such transmission line and an inductor may be realized by a proper length of shorted transmission line, (i.e. a radio frequency stub) connected in shunt to the center conductor of the coaxial transmission line. Further, such "capacitors" and "inductors" may be arranged to enable the filter formed from such coaxial transmission line to provide for matching between the impedance of the source driving such transmission line and the impedance of the load coupled to the output of such transmission line. It would sometimes be desirable to incorporate such a filter integrally with a coaxial transmission line switch; however, the coaxial transmission line switch described above does not include such an integrally formed filter.